Wrinkled Membranes and Cable-Stayed Bridges

Abstract

In seeking an efficient arrangement for the bearing cables of a cable-stayed bridge, inspiration is drawn from the natural wrinkling behavior of in-plane stressed triangular membranes. The bridge deck is thought of as being sustained by such a membrane, rather than stays, and the wrinkle pattern is studied as vertical loads act on the deck. Since it can be shown that the resulting wrinkles are straight and develop in such a way as to offer maximum stiffness towards impinging actions, the idea is to place cables according to their layout. The examined cases consider various ratios between the height of the towers and the main span of the bridge, reproducing as well the scheme of significant existing bridges and the possible presence of notches in the membrane. In all the cases, the patterns assumed by the wrinkles show evident resemblance to the traditional harp, half-fan, and fan schemes, and reveal surprising similarities with the disposal of the stays really adopted in existing bridges.